Breast cancer, which occurs in mammary tissue, is classified into lobular carcinoma arising from acini and breast ductal carcinoma arising from breast ducts. Noninfiltration breast cancer represents the state where cancer is limited within lobules or breast ducts, and cancer cells are not disseminated to surrounding tissues, whereas infiltration breast cancer represents the state where cancer cells proliferated in breast ducts destroy the basement membrane and metastasize to surrounding tissues. Adjuvant chemotherapy is an ordinary method for the treatment of breast cancer, in which an anticancer agent is administered by infusion without surgery, or after excision of an affected portion through surgery. However, many anticancer agents pose problems in that, when administered by infusion, they may cause side effects such as nausea, anorexia, and alopecia.
Mastitis is classified into stagnation mastitis and acute suppurative mastitis. Stagnation mastitis represents the state where breast ducts are congested with milk, and develops immediately after puerperium. Meanwhile, acute suppurative mastitis develops through infection with a bacterium such as Staphylococcus, Escherichia coli, or Streptococcus. Of these types of mastitis, acute suppurative mastitis has been treated with an anti-inflammatory analgesic agent.
However, such a treatment poses a problem in that a nonsteroidal anti-inflammatory analgesic agent and/or an anticancer agent cannot be administered topically, since breast cancer or mastitis occurs or develops in the breast.
Then, the present inventors conducted studies by focusing on iontophoresis, which has been known as means for enhancing percutaneous absorption, and found that when a donor of an iontophoretic preparation containing a nonsteroidal anti-inflammatory analgesic agent and/or an anticancer agent is applied to the nipple part and current is applied thereto, the topical delivery of such an active ingredient into the mammary gland is drastically improved, as compared with the case where the donor is applied to an normal skin area (e.g., a skin area of the breast) and current is applied thereto, and therefore such an iontophoretic approach is useful as means for the treatment of breast cancer and/or mastitis through topical administration. The inventors previously filed a patent on the basis of this finding (Patent Document 1).